Audio of the dispatch call from a Mandalay Bay security guard capturing the pivotal moment before Stephen Paddock opened fire on thousands of unsuspecting concert-goers in Las Vegas, Nevada, has been released.

The 24-second audio released Friday contains the voice of security guard Jesus Campos, 25, as he reports “shots fired” at Mandalay Bay from the 32nd floor of the hotel-casino.

“Hey, there are shots fired in 32-135,” Campos says, according to the audio released by MGM Resorts International.

Campos was referring to the room number where Paddock brought a large cache of weapons, and had been preparing to fire on the crowd watching the Route 91 Harvest Music Festival across the street from the hotel.

When Campos approached Paddock’s hotel room, Paddock shot him in the leg. The shooter also had cameras positioned on a cart outside his room and on his door as well. Paddock fired some 200 rounds at the door while Campos was outside. The security guard was struck one time, police said, the Los Angeles Times reported.

Paddock carried out the deadliest mass shooting in modern US history, killing 58 people, and injuring hundreds more.